1. Field of the Invention
The present invention relates to a new reproduction-only magneto-optical disk, and a reproduction method and reproduction apparatus therefor.
2. Related Background Art
In recent years, many efforts have been made to develop an optical recording/reproduction method which can satisfy various requirements including high density, large capacity, high access speed, and high recording/reproduction speed, and a recording apparatus, a reproduction apparatus, and a recording medium used therefor.
Of various optical recording/reproduction methods, the magneto-optical recording/reproduction method is most attractive due to its unique advantages in that information can be erased after it is recorded, and new information can be repetitively recorded.
A magneto-optical recording disk (medium) used in the magneto-optical recording/reproduction method has a magnetic film consisting of one or a plurality of layers. An early magnetic film was a horizontal magnetic film (the direction of magnetization is parallel to the film surface). Then, a perpendicular magnetic layer or layers having a high recording density and signal intensity were developed. Today, the latter film is adopted in almost 100% of applications. Such a magnetic layer comprises, for example, amorphous GdFe or GdCo, GdFeCo, TbFe, TbCo, TbFeCo, and the like. The perpendicular magnetic layer normally has concentric or spiral tracks, and information is recorded on the tracks. There are two types of tracks, i.e., explicit tracks and implicit tracks.